Dwarfs F2P

Guys, there's an achievement for leveling a Warrior Dwarf to level 30. I've finished (never with much sucess, i always play 60 minutes long games and water or lava ♥♥♥♥ me up) many games and the max level i got my Warriors was 17. They level up really slowly around buildings and usually there aren't many enemies around for them to kill, or if there are, it's usually really far. So my question is: How's the easiest way to get them to level 30?